// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_QUIC_CRYPTO_QUIC_ENCRYPTER_H_
#define NET_QUIC_CRYPTO_QUIC_ENCRYPTER_H_

#include <stddef.h>

#include "net/base/net_export.h"
#include "net/quic/quic_protocol.h"

namespace net {

class NET_EXPORT_PRIVATE QuicEncrypter {
public:
    virtual ~QuicEncrypter() { }

    static QuicEncrypter* Create(QuicTag algorithm);

    // Sets the encryption key. Returns true on success, false on failure.
    //
    // NOTE: The key is the client_write_key or server_write_key derived from
    // the master secret.
    virtual bool SetKey(base::StringPiece key) = 0;

    // Sets the fixed initial bytes of the nonce. Returns true on success,
    // false on failure.
    //
    // NOTE: The nonce prefix is the client_write_iv or server_write_iv
    // derived from the master secret. A 64-bit packet number will
    // be appended to form the nonce.
    //
    //                          <------------ 64 bits ----------->
    //   +---------------------+----------------------------------+
    //   |    Fixed prefix     |      packet number      |
    //   +---------------------+----------------------------------+
    //                          Nonce format
    //
    // The security of the nonce format requires that QUIC never reuse a
    // packet number, even when retransmitting a lost packet.
    virtual bool SetNoncePrefix(base::StringPiece nonce_prefix) = 0;

    // Writes encrypted |plaintext| and a MAC over |plaintext| and
    // |associated_data| into output. Sets |output_length| to the number of
    // bytes written. Returns true on success or false if there was an error.
    // |packet_number| is appended to the |nonce_prefix| value provided in
    // SetNoncePrefix() to form the nonce. |output| must not overlap with
    // |associated_data|. If |output| overlaps with |plaintext| then
    // |plaintext| must be <= |output|.
    virtual bool EncryptPacket(QuicPathId path_id,
        QuicPacketNumber packet_number,
        base::StringPiece associated_data,
        base::StringPiece plaintext,
        char* output,
        size_t* output_length,
        size_t max_output_length)
        = 0;

    // GetKeySize() and GetNoncePrefixSize() tell the HKDF class how many bytes
    // of key material needs to be derived from the master secret.
    // NOTE: the sizes returned by GetKeySize() and GetNoncePrefixSize() are
    // also correct for the QuicDecrypter of the same algorithm. So only
    // QuicEncrypter has these two methods.

    // Returns the size in bytes of a key for the algorithm.
    virtual size_t GetKeySize() const = 0;
    // Returns the size in bytes of the fixed initial part of the nonce.
    virtual size_t GetNoncePrefixSize() const = 0;

    // Returns the maximum length of plaintext that can be encrypted
    // to ciphertext no larger than |ciphertext_size|.
    virtual size_t GetMaxPlaintextSize(size_t ciphertext_size) const = 0;

    // Returns the length of the ciphertext that would be generated by encrypting
    // to plaintext of size |plaintext_size|.
    virtual size_t GetCiphertextSize(size_t plaintext_size) const = 0;

    // For use by unit tests only.
    virtual base::StringPiece GetKey() const = 0;
    virtual base::StringPiece GetNoncePrefix() const = 0;
};

} // namespace net

#endif // NET_QUIC_CRYPTO_QUIC_ENCRYPTER_H_
